Since World War II, the Mediterranean Sea has been the home to the U.S. Sixth Fleet, whose mission is to conduct “the full range of Maritime Operations and Theater Security Cooperation missions to advance security and stability in Europe and Africa.” It was an essentially uncontested naval force through the mid-2000s, operating with near impunity from the Strait of Gibraltar to Israel, from the Black Sea to the Suez Canal.

Today, Russia and China are operating within the Eastern Mediterranean region with growing ambition and determination to challenge America’s historic naval posture and extensive power projection reach.

Russia recently signed a 49-year lease with Syria, to build up its once-modest facility at Tartus into a naval base that can handle Russia’s largest nuclear-powered battle cruisers, and possibly even nuclear submarines.

Along with a long-term air base lease, Russia is building an unprecedented powerful military complex in Syria, making it possible for the first time for Russian land-based aircraft and naval forces to patrol the eastern Mediterranean without requiring support from distant home ports.

It is also the first time in 70 years that such a base complex exists in the Mediterranean beyond the control of the United States or its allies, adding the threat of sophisticated Area Access Area Denial systems, which can thwart the free flow of U.S. and allied naval and commercial vessels.

Coupled with Russia’s naval facility modernization plans in the annexed region of Crimea and its escalated diplomatic mediation between the U.N.-backed Libyan government and its military rivals in eastern Libya, Moscow is positioned to significantly influence events in the Mediterranean, and the adjoining Aegean and Black Seas, for the foreseeable future.

Similarly, China now looks to the Mediterranean Sea as the western end of its multitrillion-dollar “One Belt, One Road” infrastructure strategy, linking the Chinese economy with European and Middle Eastern markets through Central Asian land routes and Indian Ocean sea routes, including through the Suez Canal chokepoint, through which 80,000 vessels carried 1.5 million tons of shipping and energy resources in March 2017 alone.

Two years ago, Russia and China conducted their first-ever joint Mediterranean naval exercise, with nine ships engaged in anti-submarine warfare and live-fire activities as they undertook four days of cargo transfer, replenishment and escorting missions.

Further dangers emanate from Iranian proxies in Damascus, Beirut and Gaza, providing the radical Shiite state sponsor of terror with critical regional bases for malignant behavior. Islamic State retains a foothold along Libya’s eastern coast, the target of Egyptian bombardment after the most recent terror attack against Coptic Christians.

Amid the geopolitical chaos of the Eastern Mediterranean region is a single bedrock platform from which the United States and its NATO allies most effectively project military power in every direction: the U.S. Navy Strategic Forward Operating Base located in Souda Bay, on the Greek island of Crete.

Just 785 miles from Syria, 570 miles from Suez and 200 miles from eastern Libya, NSA Souda Bay routinely functions as a Naval Operating Base, Naval Air Station and Naval Weapons Station, enabling U.S. Sixth Fleet and NATO counterterrorism and anti-ballistic missile defense patrols, reconnaissance missions and air-refueling support for multinational operations such as “Odyssey Lighting” to defeat Islamic State in Libya.

Souda Bay offers the largest deep-water port in the entire Mediterranean Sea, the only one between Norfolk and the Indian Ocean that can accommodate a nuclear carrier pier-side to an airfield facility, allowing the Navy fleet to dock and carry out repairs, maintenance and resupply.

That strategic location, reinforced by Defense Secretary James Mattis when he welcomed Greece’s Defense Minister Panagiotis Kammenos to the Pentagon in March, makes Souda Bay a vital frontline station for European, African, Central, Southern and Transportation unified commands.

The Trump administration looks favorably upon Greece’s steadfast NATO commitment to defense spending exceeding 2 percent of gross domestic product, which it has maintained for more than 30 years — even in the face of the crippling economic depression of the past eight years.

The U.S. use of the Greek facilities is governed principally by the Mutual Cooperation Defense Agreement (MDCA), first signed in 1990. Since 1998, the MCDA is renewed annually.

The United States would benefit significantly from a longer-term renewal agreement with Greece, especially from a longer horizon, up to 10 years, for Souda Bay infrastructure repairs, upgrades and expansions that would enhance the American and allied strategic posture in the region.

But Washington and Athens both need long-term assurances when it comes to basing, to ensure more effective military budgetary and operational planning.

Greece is also limiting the access it offers to U.S. military planners if the mutual defense cooperation agreement is renewed only annually, rather than on a long-term basis.

The Eastern Mediterranean and Aegean Seas are of supreme importance to U.S. interests in Southeastern Europe, the Middle East, Northern Africa and the Black Sea. We now face increased regional security challenges led by the surging influences of Russia, China and Iran.

Washington and Athens should begin negotiating an updated, longer-term defense agreement that fosters even stronger bilateral military-to-military relations, strengthens the interoperability of Greek forces for NATO, and — most importantly — bolsters regional security for U.S. and allied interests, utilizing the exceptional naval facility at Souda Bay.

Such a policy would deliver to the Trump administration a more immediate and operationally effective strategic U.S. naval advantage in this increasingly dangerous corner of the globe.